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/*
* Copyright (C) 2013 Google, Inc. All Rights Reserved.
* Copyright (C) 2015 Apple Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef WTF_WeakPtr_h
#define WTF_WeakPtr_h
#include <wtf/Noncopyable.h>
#include <wtf/Ref.h>
#include <wtf/ThreadSafeRefCounted.h>
#include <wtf/Threading.h>
#if USE(WEB_THREAD)
#include <wtf/MainThread.h>
#endif
namespace WTF {
template<typename T> class WeakPtr;
template<typename T> class WeakPtrFactory;
// Note: WeakReference is an implementation detail, and should not be used directly.
template<typename T>
class WeakReference : public ThreadSafeRefCounted<WeakReference<T>> {
WTF_MAKE_NONCOPYABLE(WeakReference<T>);
WTF_MAKE_FAST_ALLOCATED;
public:
T* get() const
{
#if USE(WEB_THREAD)
ASSERT(canAccessThreadLocalDataForThread(m_boundThread));
#else
ASSERT(m_boundThread == currentThread());
#endif
return m_ptr;
}
void clear()
{
#if USE(WEB_THREAD)
ASSERT(canAccessThreadLocalDataForThread(m_boundThread));
#else
ASSERT(m_boundThread == currentThread());
#endif
m_ptr = nullptr;
}
private:
friend class WeakPtr<T>;
friend class WeakPtrFactory<T>;
static Ref<WeakReference<T>> create(T* ptr) { return adoptRef(*new WeakReference(ptr)); }
explicit WeakReference(T* ptr)
: m_ptr(ptr)
#ifndef NDEBUG
, m_boundThread(currentThread())
#endif
{
}
T* m_ptr;
#ifndef NDEBUG
ThreadIdentifier m_boundThread;
#endif
};
template<typename T>
class WeakPtr {
WTF_MAKE_FAST_ALLOCATED;
public:
WeakPtr() : m_ref(WeakReference<T>::create(nullptr)) { }
WeakPtr(const WeakPtr& o) : m_ref(o.m_ref.copyRef()) { }
template<typename U> WeakPtr(const WeakPtr<U>& o) : m_ref(o.m_ref.copyRef()) { }
T* get() const { return m_ref->get(); }
operator bool() const { return m_ref->get(); }
WeakPtr& operator=(const WeakPtr& o) { m_ref = o.m_ref.copyRef(); return *this; }
WeakPtr& operator=(std::nullptr_t) { m_ref = WeakReference<T>::create(nullptr); return *this; }
T* operator->() const { return m_ref->get(); }
void clear() { m_ref = WeakReference<T>::create(nullptr); }
private:
friend class WeakPtrFactory<T>;
WeakPtr(Ref<WeakReference<T>>&& ref) : m_ref(std::forward<Ref<WeakReference<T>>>(ref)) { }
Ref<WeakReference<T>> m_ref;
};
template<typename T>
class WeakPtrFactory {
WTF_MAKE_NONCOPYABLE(WeakPtrFactory<T>);
WTF_MAKE_FAST_ALLOCATED;
public:
explicit WeakPtrFactory(T* ptr) : m_ref(WeakReference<T>::create(ptr)) { }
~WeakPtrFactory() { m_ref->clear(); }
// We should consider having createWeakPtr populate m_ref the first time createWeakPtr is called.
WeakPtr<T> createWeakPtr() const { return WeakPtr<T>(m_ref.copyRef()); }
void revokeAll()
{
T* ptr = m_ref->get();
m_ref->clear();
// We create a new WeakReference so that future calls to createWeakPtr() create nonzero WeakPtrs.
m_ref = WeakReference<T>::create(ptr);
}
private:
Ref<WeakReference<T>> m_ref;
};
} // namespace WTF
using WTF::WeakPtr;
using WTF::WeakPtrFactory;
using WTF::WeakReference;
#endif
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